Weighting Function Integrated in Grid-interfacing Converters for Unbalanced Voltage Correction

In this paper a weighting function for voltage unbalance correction is proposed to be integrated into the control of distributed grid-interfacing systems. The correction action can help decrease the negative-sequence voltage at the point of connection with the grid. Based on the voltage unbalance factor and system power capacity, the interfacing converter delivers a small amount of negative-sequence current to the grid and helps correcting the negative-sequence voltage. Although the reduced amplitudes contributed by each individual DG system are very small compared to the total negativesequence component, many DG system modules can collectively achieve substantial results in the grid. As a practical example, a three-phase grid-interfacing converter servicing sensitive loads with distributed sources is employed to integrate this additional function. Design principles, simulation and experimental results are presented to verify the proposal.